Froogle only comes up with one vendor:
http://www.partstore.com/Part/Apple Computer Incorporated/Apple/922-4030/Refurbished.aspx?s=froogle
But there is also this one - quite a bit cheaper but still expensive:
iMac Slot Load Hard Drive Power Cable $17.77
Have you tried these places? There are probably others if you search a bit more. This was just a 30 second exercise with Froogle and Google to get those two.